This invention relates to access stairways for aircraft foldable and stowable on board the craft and further relates to such stairways interconnected with an access doorway for coordinated opening of the door and stair.
The advent of large commercial and military aircraft such as the so called "wide body" jet transports necessitates access to the lower lobe portion of the craft by personnel for such functions as stowing cargo and baggage, equipment servicing and similar activities. In addition, usage of large aircraft for the transport of large numbers of passengers may require usage of the lower portion of the craft for passenger seats as well as the presently contemplated centrally located passenger deck. It is well known to use stowable folding on board air stairs for access to passenger compartments in smaller aircraft, such as is shown in U.S. Pat. No. 2,531,263 issued to F. W. Fink et al., Nov. 21, 1950. While this device employs a counterbalance between the door and the stair to minimize effort exerted by the operator in opening and closing the apparatus, the door must first be completely or nearly completely be opened before the stair can be extended and retracted and therefore direct mechanical coaction between the stair and the door is not feasible. The counterbalancing effect is obtained through usage of a spring means to store the energy obtained through movement of the door initially which is then transmitted to the movable stairway.
Having the door positioned on the lower lobe area of an aircraft further compounds the problem of coaction of the door and stair. Due at least in part to the geometrical configuration of a lower lobe door and stair combination, a direct interlinkage of the door and stair operating mechanisms has heretofore not been practiced.